A number of methods exist in the prior art for producing electronic devices from a semiconductor wafer. For example in DE 40 20 195, there is disclosed a process wherein electronic devices having active regions are formed on a semiconductor wafer, and separation regions are provided between the electronic devices for separating the latter. By forming a saw line, the separation regions are patterned. The electronic devices also include a depression and are separated by sawing along the saw lines.
Such a process is also disclosed in DE 43 17 721. There, the separation regions between the electronic devices are patterned by etching. This process uses an SOI (silicon-on-insulator) substrate. The electronic devices are separated by etching away the insulator layer.
After the electronic devices have been separated from the semiconductor wafer, they must be brought into contact with external arrangements, such as lead frames and/or printed circuit boards. The necessary contact pads are located on the surface of the electronic devices. The electronic devices are connected to the external arrangement by bonding techniques or by a flip-chip technology. Both methods are complicated and costly and involve various disadvantages. For instance, high mechanical stresses are induced in the electronic devices. The electronic devices must have a minimum height in order to withstand the mechanical loads during the mounting or bonding operations. Separate bonding pads must be provided for making contact to the electronic devices. Only a few materials are suitable for such pads. Further, flip-chip technology has the disadvantage that the electronic devices are not always suitable for use as sensors, since their surface is difficult to access for signal extraction. Problems are also encountered in processing the individual electronic devices after the separation step.
In U.S. Pat. No. 3,639,811 issued to Schroeder on Feb. 1, 1972, entitled "Semiconductor with Bonded Electrical Contact", a method for separation is disclosed wherein a sawing process is necessary for separating the side walls of the electronic elements. Thereafter, they are separated by mechanical pressure so that the terminals are separated from the adjacent electronic element. A disadvantage of this technique is that the terminals of the adjacent chips are out of line. Therefore, different types of chips are formed on the same wafer which leads to difficulties in the mounting process of the chips. Further, the combined sawing and pressure process is less precise and reliable than desired, since terminals can be easily damaged via the sawing process, requiring material to remain between elements.
Accordingly, it is highly desirable to obtain a process for producing electronic devices having conductive terminals via which the electronic devices can be better connected to external arrangements.